The overall goal of this project is to understand how the strength of TCR signalling influences Th2 cell generation. The focus will be on two specific aims: 1) Analysis of the role of CD4 in Th2 differentiation and 2) characterization of IL-4 receptor function during Th differentiation induced by peptides of differing affinity for the T-cell receptor. In vivo studies of immune responses to infectious diseases have indicated that protection against infection is critically dependent on generating the appropriate immune responses and leads to nonhealing lesions and a deficiency in pathogen clearance. Furthermore, many autoimmune diseases are characterized by Th1 destructive responses. Therefore, a critical aspect in addressing inappropriate Th1 or Th2 responses is understanding what factors influence the generation of each type of effector cell responses.